Rotating sorters or sizers, commonly called separators, are well known in the art of classifying particulate matter, such as seeds, grains, stones, etc., by their size. Such separators typically include a housing that supports a rotatable cylinder. The "cylinder" usually has a tubular configuration, though any structure having a regular polygonal cross section would suffice. The cylinder includes a frame structure comprising a pair of end rings that support either a single sizing unit conforming to the frame structure or individual panel sections attached to the frame structure and to each other. Representative examples of such rotating separators can be found in U.S. Pat. No. 779,149 to Cross; U.S. Pat. No. 1,284,669 to Haug; U.S. Pat. No. 1,427,031 to Stepp; U.S. Pat. No. 2,204,835 to Traylor; U.S. Pat. No. 4,184,944 to Tytko; U.S. Pat. No. 4,222,865 to Valeri et al.; U.S. Pat. No. 4,670,136 to Schmidt et al.; U.S. Pat. No. 5,049,262 to Galton et al.; U.S. Pat. No. 5,213,217 to Galton et al.; U.S. Pat. No. 5,346,071 to Page et al; and U.S. Pat. No. 5,507,396 to Hauch. Such separators can be classified into two general types: those with sizing panels that size the particulate matter with the use of holes through which the particles smaller than the holes fall and those with panels having clefts or indentations that capture the smaller sized particles and rotationally carry them away from the larger particles.
In a typical operation of the latter type of separator, the granular material to be sorted is fed into the interior of the rotating cylinder of the separator. There, material less than a predetermined size is "captured" within indentations or clefts in the cylinder and carried upwardly and rotationally away from the larger material particles, which remain in the lower portion of the separator. As the captured particles near or reach the apex of the rotational motion of the cylinder, they fall downwardly under gravitational influence into an auger, which carries them away to be disposed of or utilized as desired. The larger sized particles are then carried out of the rotating cylinder. It will be appreciated that the size of the particles sorted is dependent upon the size of the cylinder indentations.
Separators having a single, unitary cylinder panel with two longitudinally attached edges are generally easily attached to the separator frame. The single panel cylinder separators, can present structural fatigue problems, however. These separator cylinders generally have a tubular configuration and present two circumferential edges at opposite ends for attachment to a pair of end rings on the separator frame. Additionally, the screen has two longitudinal edges that are attached to each other.
In operation, as the cylinder rotates, the weight of the material being sorted is constantly being transferred to that portion of the cylinder at the lowest point of the rotation. This rotating, cylinder-flexing load thus causes the cylinder to continuously flex downwardly. As just mentioned, the cylinder is often attached only along its circumferential edges to the frame structure. Thus, the shifting load carried by the cylinder has been known to fatigue the cylinder along its circumferential edges, causing the creation of cracks along those very edges. Stated otherwise, in the known prior art single cylinders as the separator was rotated, the cylinder would continuously deform with each revolution thereof, leading to life cycle fatigue and cracking along the attached circumferential edges.
Because of the loading problems just discussed, hoops are often welded to the exterior surface of the separator cylinder to provide additional support. While the hoops function generally as intended, the hoops also add mass that must be rotated by the motor rotationally driving the separator cylinder, thus creating additional wear and tear on the motor. Additionally, the extra weight of the hoops requires the use of stronger bearing support structures. Another disadvantage of this construction is that welding or otherwise attaching the hoops to the outer surface of the separator cylinder entails another manufacturing step that increases the cost of manufacture in terms of time, manpower, and materials cost. An improvement in the separator art relating to trommels, that is, to separators having screens with holes, is shown in the foregoing Hauch '396 patent.
To avoid this loading problem and the life cycle fatigue created by a single cylinder panel, many of the devices disclosed in the prior art have utilized a multiple cylinder panel construction. In a typical multiple panel cylinder construction, the cylinder would be formed from at least two, and usually three or more, panel sections that would be individually attached to the end rings along their circumferential edges. In addition, the panel segments would be attached to each other along adjoining longitudinally extending edges. This reduces the prior art loading problem, but the prior art cylinder panel sizer constructions are complex, making their construction and maintenance difficult.
Prior art designs are also subject to leaking along the joints between sizing panels as a result of an inability to adequately accommodate size variations in the sizing panels. For example, in prior art methods of attaching sizing panels the panels are secured substantially parallel to a tangent to the cylinder circumference, which inhibits the ability of the design to accommodate size variations. In addition, in prior art designs, the flanges are used for attachment to each other, with the circumferential edge only being attached to the rotating frame since there are no stringers present in this design. Consequently, any dimensional variation in the sizing panels is accommodated through the use of sealing gaskets installed between the attached flanges. With this prior art design, however, the bolts used to attach the flanges to each other are often over tightened. This overtightening can distort the flanges, which can in turn can cause the particulate matter being sized to leak out of the cylinder along the attachment joint.
It would be desirable to have a sizer or separator that utilizes multiple cylinder panels to reduce the fatigue caused by the rotating load but that is simpler in construction, that is easier to install and take apart for maintenance, that costs less to build than the prior art structures, and that is less susceptible to joint leakage.